||Name|Title Reign|Title Recognition|Successful Defenses|
|---|---|---|---|---|
|1.|Joe Calzaghe|10 years, 11 months, 15 days|IBF, WBA, WBO, WBC, The Ring|21|
|2.|Sven Ottke|5 years, 5 months, 3 days|IBF, WBA (Super)|21|
|3.|Frankie Liles|4 years, 10 months, 0 days|WBA|8|
|4.|Lucian Bute|4 years, 7 months, 7 days|IBF|9|
|5.|Chris Eubank|4 years, 4 months, 0 days|WBO|14|
|6.|Andre Ward|4 years, 6 months, 3 weeks and 1 day|WBA (Super), WBC, The Ring|6|
|7.|Chong-Pal Park|3 years, 7 months, 17 days|IBF, WBA|10|
|8.|Nigel Benn|3 years, 4 months, 28 days|WBC|9|
|9.|Robert Stieglitz|3 years, 0 months, 3 days|WBO|6|
|10.|Mikkel Kessler|2 years, 11 months, 23 days|WBA (Super)|4|

Question: what is the difference between the number of successful defenses by joe calzaghe and robert stieglitz?
Answer: 15